This invention relates to improvements in the ammunition art and, specifically, to ammunition cartridges of the type having a plastics cartridge case, i.e. a case that is made, at least in a predominant portion, of a synthetic polymer composition and where the lower end portion of the cartridge case is provided with a bottom insert made of a metal. The term "lower end" relates to that end of the cartridge case which is opposed to the projectile-bearing or projectile imitation-bearing end of the cartridge.
Cartridges of this type are known and have been disclosed, for instance, in Swiss Patent 326,592. Cartridges of this type are used in large quantities as blank rifle cartridges in which the head end of the cartridge case continues into the imitation shape of a plastics projectile which constitutes an integral part of the cartridge case and is furnished at its upper end with a notch or similarly formed predetermined rupture point.
The use of a plastics material for ammunition cartridge cases offers considerable advantages over usual metal cases in regard to cost and production, but necessitates a bottom insert of metal which is suitable as a groove or edge for engaging the usual cartridge extractor and ejector and for receiving and holding a detonator or percussion cap.
A prior art bottom insert of this type is a generally cylindrically shaped, solid metal component having an opening for receiving the detonator cap, an external groove for interaction with the cartridge extractor, and a generally cylindrical upper end portion with its external surface grooved in the manner of a dowel for anchoring inside the wall of a plastics cartridge case. Generally, such bottom inserts are made from aluminum by machining as relatively large thicknesses of material are required in the cartridge bottom. Thus, production of conventional all-metal bottom inserts for plastics cartridges tends to be relatively costly both in view of the comparatively large mass of metal required and the costs of producing the inserts by conventional machining techniques. Insertion of such metal inserts into a plastics cartridge case can present problems such as ruptures of the walls of the plastics cartridge case. Further problems in connection with ammunition cartridges of the type having a plastics case for blank cartridges or projectile-bearing cartridges are encountered in regard to the projectile-like end portion or the connection of the projectile and the plastics cartridge case.